1. Field of the Invention
The present invention relates to a shift control system for an automatic transmission that can be operated not only under an automatic shift mode, but also under a manual shift mode.
2. Description of Related Art
Such an automatic transmission is highly suitable for various purposes ranging from ordinary use to sporty use, since a proper gear ratio can be selected not only automatically according to a shift command based on a throttle valve opening and a vehicle speed, but also manually according to a shift command given by driver""s manual operation in a fun-to-drive manner. Prior attempts at this type of automatic transmission suffer from a problem that multiple shift commands may be successively given within a short period causing noticeable shift shocks and thereby degrading driving comfort. Thus, in an attempt to mitigate shift shocks and/or avoid degradation of the driving comfort, a shift control system is proposed in JP 6-323418A, which includes a system designed such that, during a shift operation corresponding to input of a shift command, a further shift operation based on a subsequent shift command is prohibited when a predetermined time or so-called xe2x80x9cre-shift permission timexe2x80x9d has elapsed. However, even if the intended objectives can be more or less achieved by such a conventional solution, there still remains a problem often felt by many drivers, that a satisfactory response to shift command is not achieved particularly in the manual shift mode wherein an immediate reaction of the transmission is desired after a shift command is manually given.
It is therefore a primary object of the present invention to provide an improved shift control system for an automatic transmission having an automatic shift mode and a manual shift mode, wherein the shift control system is so designed as to achieve a sufficient response to shift command in the manual shift mode, while mitigating shift shocks and/or avoiding degradation of the driving comfort.
The inventors conducted thorough research and investigations and arrived at a recognition that the above-mentioned problems of the prior art resulted from the design of the shift control system in which the length of the re-shift permission time for automatic shift operation and that for manual shift operation are the same. In other words, it has been conceived by the inventors that the shift control, both in the automatic shift mode and the manual shift mode, can be optimized if different re-shift permission times are set for these two shift modes.
According to the present invention, there is provided a shift control system for an automatic transmission having an automatic shift mode in which a proper gear ratio is automatically selected according to a shift command based on a throttle valve opening and a vehicle speed, and further having a manual shift mode in which a gear ratio is selected according to a shift command given by driver""s manual operation, wherein the shift control system comprises timer means for counting an elapsed time after a shift operation has been started, which elapsed time is compared with a predetermined first re-shift permission time in the case of automatic shift operation and with a predetermined second re-shift permission time in the case of manual shift operation, wherein the first re-shift permission time and the second re-shift permission time are different from each other.
In the shift control system according to the present invention, an elapsed time after a shift operation has been started is counted by a timer means and compared with a predetermined first re-shift permission time in the case of automatic shift operation and with a predetermined second re-shift permission time in the case of manual shift operation, wherein the first re-shift permission time and the second re-shift permission time are different from each other. Therefore, it is possible to perform the shift control in optimized manner both in the automatic shift mode and the manual shift mode.
It is preferred that the second re-shift permission time is set to be longer than the second re-shift permission time. In this instance, it is possible to perform the shift control, by giving priority to avoidance of shift shocks and/or degraded driving comfort, in the case of automatic shift mode, and further giving priority to response to a shift command in the case of the manual shift mode.
It is preferred that the manual shift mode of the automatic transmission enables an upshift of one step of the gear ratios by one manual operation and a downshift of one step of the gear ratios by one manual operation. In this instance, even when the driver in the manual shift mode of the transmission successively gives multiple commands for upshift and/or downshift operations within a short time, the shift operation exactly to a gear ratio as intended by the driver can be performed with a satisfactory response.